The present invention is in the field of electrical generators and motors and, more particularly, electrical starter generators operating at very high rotational speeds.
In certain applications of generators such as those employed in aircraft, there is a requirement to produce a high power density with a generator that is small in size and light in weight. In these applications, a desired high power density may be achieved with relatively small generators which operate at very high rotational speeds. A typical aircraft generator may operate at rotational speeds of 12,000 to 24,000 rpm.
When a generator is operated at such high rotational speeds, rotatable components of the generator may be subjected to correspondingly high centrifugal forces. Some rotatable components may be particularly vulnerable to damage from centrifugal forces and fatigue. Examples of these vulnerable components are interconnections between field coils of the generators.
In a typical aircraft high-speed generator, field coils may be interconnected to one another with crossovers. Fatigue inducing stresses may arise in crossovers because high rotational speeds and temperatures of the aircraft generators produce a radial displacement of the field coils relative to an axis of rotation. This radial displacement may cause variation of circumferential spacing between the field coils. While such spacing variation may be relatively small, it is nevertheless large enough to produce bending of the crossover during each change of rotational speed of the generator. Repeated bending of the flat strip crossovers may produce stresses which may lead to fatigue failure of the crossovers.
As can be seen, it would be desirable to construct high-speed generators which do not incorporate crossovers that are vulnerable to fatigue failure. Additionally, it would be desirable to provide a method for constructing such generators without producing work hardening of the crossover or wicking of brazing filler metal into the crossover.